By recent research and development, a hybrid car and an electric car are practically used. As a secondary battery for the cars, there is utilized a high capacity and high power secondary battery (hereinafter referred to as a battery) such as a nickel-metal hydride secondary battery or a lithium ion secondary battery.
In the utilization of the secondary battery in earnest, a large number of used secondary batteries are generated by the scrap of a car, an exchange of a battery (a battery unit) or the like. However, it can be supposed that some used secondary batteries have a failure, have defective characteristics, or run down, but include a large number of batteries still usable. In respect of an environmental demand, an effective utilization of resources or energy for manufacturing a battery and the like, it is required to properly recycle the used secondary battery. Moreover, there can also be supposed the case in which a brand-new battery is not utilized but a used secondary battery is used in order to remove a particular battery that has a failure or is greatly deteriorated from a battery unit and to replace the battery with another one.